Refrigerant evaporator



Sept. 5, 1961 J. E. WATKINS REFRIGERANT EVAPORATOR Filed Oct. 31, 1957INVENTOR. 70a 51% [125' az zfys'.

2,998,712 REFRIGERANT EVAPORATOR John E. Watkins, 1311 S. 4th Ave.,Maywood, Ill. Filed Oct. 31, 1957, Ser. No. 693,668 4 Claims. (Cl.62278) The present invention relates generally to refrigerating systemsand more particularly to evaporators for use in such systems.

It is an object of the invention to provide in a refrigerating system ofthe compressive process type refrigerant evaporator means of improvedconstruction and arrangement which permits o-f economical manufacture,which is efiicient in operation, and which facilitates defrosting.

Another object is to provide a new and improved construction for arefrigerant evaporator which affords complete coil utilization forrefrigerating operation and which is effective to insure completedefrosting not only of the coils but also of the associated drain pan.

A further object of the invention is to provide for incorporation in arefrigerating system having a liquid refrigerant supply line, a suctionline and a hot gas line, a refrigerant evaporator of improvedconstruction together with control valve means operable to direct liquidrefrigerant through all of the evaporator coils during normalrefrigerating operation and alternatively to direct hot gas through thedefrosting coil to clear the drain pan of frost and ice and then throughthe cooling coils for defrosting them.

The objects of the invention thus generally set forth together withother objects and ancillary advantages are attained by the constructionand arrangement shown in the accompanying drawing, in which:

FIGURE 1 is a perspective view of an evaporator embodying the featuresof the present invention.

FIG. 2 is a central vertical section taken substantially in the plane ofline 2--2 in FIG. 1 and including 9. diagrammatic representation of atypical compressive process type refrigerating system.

While the invention is susceptible of various modifications andalternative constructions, there is shown in the drawing and will hereinbe described in detail a preferred embodiment. It is to be understood,however, that it is not intended to limit the invention to the specific:form disclosed. On the contrary, it is intended to embrace allmodifications and alternative constructions fall ing within the spiritand scope of the appended claims.

Referring more particularly to the drawings, there shown for purposes ofillustration is a refrigerant evaporator embodying the features of thepresent invention. The evaporator, which is generally designated by thereference numeral 10, includes a plurality of cooling coils 12. Each ofthe coils 12 preferably consists of continuous tubing formed intosuccessive longitudinal runs 12a which are uniformly spaced and areconnected by smoothly rounded reentrant or bight portions 12b. As shownthe coils 12 are vertically disposed and in laterally spaced relation toeach other, being so maintained and supported by a large-number oftransverse fins 14. The fins are formed of heat conducting material suchas sheet metal, and each is intimately connected with the coil tubing.The individual fins are spaced apart and provide heat exchange surfacesover which the fluid medium, such as air, which is to be cooled, ispassed.

. The terminal ends of the coils '12 are interconnected, or manifolded,by transversely disposed headers 16 and 18. Thus the coils 12 arearranged to provide for parallel fluid flow therethrough. To facilitatemounting of the evaporator the finned coil bank is provided at its endswith spaced support members 20 here shown to be of channel form. Theinlet and outlet headers 16 and Patented Sept. 5, 1961 2 18,respectively, are preferably formed of somewhat heavier material thanthat of the coil tubing and are fixed at their ends to the supports 20for purposes of strength and to minimize application of strain to thejunctions between the terminal ends of the coils 12 and the headers.

During refrigerating operation frost forms on the coils and on the fins.This frost has an insulating effect and should be removed in order toobtain efficient refrigerating operation. For this purpose defrosting isperiodically effected during which the accumulated frost melts and runsoff the fins and coils. To catch the melted frost a drain pan 22 isprovided. The drain pan is of shallow tray form and extends entirelybeneath the finned coil bank of the evaporator. The drain pan 22 beingdisposed beneath the finned coil bank may, if desired, be supported insuch position by suspension bolts (not shown) and the supports 20 areequipped with sleeves 24 to receive'such bolts. The drain pan 22 isprovided with a runoff pipe 26 to convey away the melted frost.

To facilitate defrosting of the evaporator and particularly to insuremelting of any ice which might have formed in the drain pan duringpreceding refrigerating operation a defrosting coil 28 is provided. Thedefrosting coil is disposed beneath the cooling coils 12 and adjacentthe drain pan 22. As shown, the defrosting coil includes a plurality ofparallel runs 28a of tubing .corresponding in number and spacing to thecooling coils. The tubing runs 28a extend through and are joined to thefins 14 and are interconnected at their ends by headers 30 and 32. Theheaders '30 and 32 are fixed at their ends to the support members 20.

In accordance with one aspect of the present invention all of the coilsincluding the cooling coils 12 and defrosting coil 28 of the evaporatorare utilized for cooling during refrigerating operation. To this end theupper cooling coil header 18 and the defrosting coil header 30 areinterconnected by a conduit 34. Desirably these two headers of theconduit may be formed of a continuous length of tubing joined bysmoothly rounded corner bends disposed just outside of the 'web portionof one of the channel support members 20 with the conduit portion 34being disposed between its flanges.

The improved evaporator is intended primarily for incorporation in arefrigerating system of the compressive process type. For purposes ofillustration such a system has been diagrammatically indicated in FIG.2. It includes a compressor 36, a condenser 37, and a liquid refrigerantreceiver 38 as well as the evaporator 10. A liquid refrigerant supplyline 39 is connected between the receiver 38 and the inlet cooling coilheader 16 for supplying liquid refrigerant to the cooling coils :12 forflow therethrough from bottom to top and thence by way of the conduit 34to the header 30 for flow through the defrosting coil. This refrigerantfluid flow is indicated in FIG. 2 by dotted arrows. So as to providea-return for spent refrigerant from the evaporator, the suction line 40to the compressor 36 is connected to the defrosting coil header 32. Fromthe compressor the refrigerant is delivered by wayof a hot gas line41-to the condenser 37.

For defrosting operation hot gas from the compressor is applied to theevaporator. Desirably the hot gas is supplied first to the defrostingcoil 28 and thence, by way of the conduit 34 to'the header 18 andthrough the cooling coils 12 from which it is returned by way of the Tocomplete the hot gas return to the suction line 40 a bypass conduit 42is interposed between the liquid refrigerant supply line 39, adjacentthe cooling coil header 16 and the suction line 40.

Valve means is provided for controlling refrigerant fluid flow. Thisvalve means is normally operable for refrigerating operation to supplyliquid refrigerant to the inlet ends of the cooling coils 12 by way ofthe header 16 and is alternatively operable for interrupting the supplyof liquid refrigerant and for connecting the defrosting coil to the hotgas line and for connecting the header 16 so as to discharge from thefinned coil bank any liquid such as refrigerant remaining from apreceding refrigerating cycle or any hot gas condensate, as shown, tothe suction line 40. It will be understood, of course, that the valvemeans may take any suitable form. Thus the valve means may consist offour independent valves manually, mechanically, or electrically operatedor they may be combined. For purposes of illustration and ease ofunderstanding four independent valve elements have been diagrammaticallyindicated in FIG. 2. Thus there is shown a valve 44 in the liquidrefrigerant supply line 39. A second valve 45 is included in the suctionline 40. A third valve 46 is included in the hot gas line 41a and afourth valve 47 is included in the bypass line 42.

For normal refrigerating operation the liquid refrigerant supply linevalve 44 and the suction line valve 45 are open. For such operation thehot gas line valve 46 and the bypass line valve 47 are closed. Uponreference to FIG. 2, therefore, it will be seen that refrigerant fluidflow will be in accordance with the dotted arrows. For defrostingoperation the liquid refrigerant supply is interrupted by closing thevalve 44. The hot gas line valve 46 is opened to supply hot gas, andreturn to the compressor is effected by opening the bypass line valve 47and closing the suction line valve 45. Thus it will be seen that fluidflow for defrosting operation is effected as indicated in FIG. 2 by thesolid arrows.

From the foregoing it will be apparent that a refrigerant evaporatorconstructed in accordance with the present invention permits ofeconomical manufacture, is efficient in operation, and insures completedefrosting. The integral, dual-purpose, defrosting coil effectivelyfunctions as an additional cooling coil so that all of the coils of theevaporator are utilized during refrigerating operation. This, it will beseen, increases the effective capacity of the evaporator through theprovision of additional evaporator surface for refrigerating operationwithout increasing the overall size of the unit. The

disposition of the defrosting coil below the cooling coils and adjacentthe drain pan together with the supply of hot gas first thereto andthence through the cooling coils as described insures that ice and frostin the drain pan formed during preceding freezing operation is melted sothat it can drain off and the operation of the drain pan and its runoffpipe to collect and convey away melted frost during defrosting isunimpeded. Furthermore, the disposition of the defrosting coil beneathand immediately adjacent to the cooling coils with subsequent connectionto the upper cooling coil header effectively decreases dcfrosting time.

I claim as my invention:

1. In a refrigerating system having a liquid refrigerant supply line, asuction line, and a hot gas line, the

combination comprising an evaporator including cooling coilsinterconnected at their upper and lower terminal ends, a defrostingcoil, a drain pan disposed adjacent said defrosting coil for receivingmelted frost from said coils, a conduit interconnecting the upper endsof the cooling coils and one end of the defrosting coil, a normally openliquid refrigerant supply valve for connection with the liquidrefrigerant supply line, a second conduit interconnected between saidliquid refrigerant supply valve and the lower ends of said coolingcoils, a normally open suction control valve for connection in thesuction line, a third conduit interconnecting said suction control valveand the other end of said defrosting coil, a normally closed hot gassupply valve for connection in the hot gas supply line, a fourth conduitinterposed between said hot gas supply valve and said third conduit, abypass line including a normally closed bypass valve interconnectingsaid second conduit and the suction line, said valves in their normalpositions effecting refrigerating operation by supplying liquidrefrigerant to said lower ends of the cooling coils and thence by way ofsaid first conduit and said defrosting coil to the suction line, andsaid valves in their alternative position effecting defrosting operationby supplying hot gas to the other end of said defrosting coil first andthence by way of said first conduit to the upper ends of said coolingcoils, and from the cooling coils to the suction line by way of thelower ends of the cooling coils.

2. In a refrigerating system having a liquid refrigerant supply line, asuction line and a hot gas line, the combinationcomprising an evaporatorincluding a plurality of cooling coils interconnected at their upper andlower terminal ends, a defrosting coil disposed beneath said coolingcoils, a conduit interconnecting the upper ends of the cooling coils andone end of the defrosting coil, and valve means having alternativepositions for supplying in one position thereof liquid refrigerant tothe lower interconnected terminal ends of said cooling coils and thenceby way of said conduit and said defrosting coil to the suction line ofthe refrigerating system for refrigerating operation, and in the otherposition thereof for interrupting the supply of liquid refrigerant, forconnecting the other end of said defrosting coil to said hot gas line,and for connecting the lower ends of said cooling coils to the suctionline of the refrigerating system whereby during defrosting operation hotgas is supplied first to said defrosting coil and thence by way of saidconduit to said cooling coils.

3. An evaporator for use in a refrigerating system having a liquidrefrigerant supply line, a suction line and a hot gas line, saidevaporator comprising, in combination, a plurality of verticallydisposed cooling coils of refrigerant conducting tubing supported inlaterally spaced relation, an upper header interconnecting the upperterminal ends of said cooling coils, a lower header for alternativeconnection to the liquid refrigerant supply line and suction line of therefrigerating system and interconnecting the lower terminal ends of saidcooling coils, a horizontal defrosting coil disposed beneath the coolingcoils and including spaced longitudinal runs of tubing, said defrostingcoil having a rear header for alternative connection to the suction lineand the hot gas line of the refrigerating system and interconnecting therear ends of said tubing runs, said defrosting coil further having afront header interconnecting the front ends of said tubing runs, and aconduit directly connecting said upper and front headers, whereby all ofsaid coils including said cooling coils and said defrosting coil conductrefrigerant during refrigerating operation, and during defrostingoperation said defrosting coil first receives hot gas.

4. In a refrigerating system having a liquid supply line, a suction lineand a hot gas line, the combination comprising an evaporator including aplurality of cooling coils, a first header interconnecting the inletterminal ends of said coils, a second header interconnecting the outletterminal ends of said coils, a defrosting coil disposed beneath saidcooling coils, a conduit interconnecting said outlet header and one endof said defrosting coil, and valve means having alternative positionsfor supplying in one position thereof liquid refrigerant to said inletheader and thence by way of said cooling coils, said conduit and saiddefrosting coil to the suction line of the system for normalrefrigerating operation, and in the other position thereof forinterrupting the supply of liquid References Cited in the file of thispatent UNITED STATES PATENTS Zellhoefer Nov. 29, 1938 Philipp Nov. 19,1940 Smith Mar. 24, 1953 La Porte June 16, 1953 Philipp Oct. 18, 1955

